When: During a pre-defined DBA maintenance windows. Tuesday 12th April at 06:00 AM UTC
Affected wikis:: commonswiki testcommonswiki
Checklist:
NEW primary: db1160
OLD primary: db1138
- Check configuration differences between new and old primary:
sudo pt-config-diff --defaults-file /root/.my.cnf h=db1138.eqiad.wmnet h=db1160.eqiad.wmnet
Failover prep:
- Silence alerts on all hosts:
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s4 T304933" 'A:db-section-s4'
- Set NEW primary with weight 0
sudo dbctl instance db1160 set-weight 0 sudo dbctl config commit -m "Set db1160 with weight 0 T304933"
- Topology changes, move all replicas under NEW primary
sudo db-switchover --timeout=15 --only-slave-move db1138 db1160
- Disable puppet on both nodes
sudo cumin 'db1138* or db1160*' 'disable-puppet "primary switchover T304933"'
- Merge gerrit puppet change to promote NEW primary: https://gerrit.wikimedia.org/r/c/operations/puppet/+/778688/
Failover:
- Log the failover:
!log Starting s4 eqiad failover from db1138 to db1160 - T304933
- Set section read-only:
sudo dbctl --scope eqiad section s4 ro "Maintenance until 06:15 UTC - T304933" sudo dbctl config commit -m "Set s4 eqiad as read-only for maintenance - T304933"
- Check s4 is indeed read-only
- Switch primaries:
sudo db-switchover --skip-slave-move db1138 db1160 echo "===== db1138 (OLD)"; sudo db-mysql db1138 -e 'show slave status\G' echo "===== db1160 (NEW)"; sudo db-mysql db1160 -e 'show slave status\G'
- Promote NEW primary in dbctl, and remove read-only
sudo dbctl --scope eqiad section s4 set-master db1160 sudo dbctl --scope eqiad section s4 rw sudo dbctl config commit -m "Promote db1160 to s4 primary and set section read-write T304933"
- Restart puppet on both hosts:
sudo cumin 'db1138* or db1160*' 'run-puppet-agent -e "primary switchover T304933"'
Clean up tasks:
- Clean up heartbeat table(s): delete from heartbeat.heartbeat where server_id=171978876
- change events for query killer:
events_coredb_master.sql on the new primary db1160 events_coredb_slave.sql on the new slave db1138
- Update DNS: https://gerrit.wikimedia.org/r/c/operations/dns/+/778689/
- Update candidate primary dbctl and orchestrator notes
sudo dbctl instance db1138 set-candidate-master --section s4 true sudo dbctl instance db1160 set-candidate-master --section s4 false (dborch1001): sudo orchestrator-client -c untag -i db1160 --tag name=candidate (dborch1001): sudo orchestrator-client -c tag -i db1138 --tag name=candidate
- Check zarcillo was updated
- db-switchover should do this. If it fails, do it manually: https://phabricator.wikimedia.org/P13956
- (If needed): Depool db1138 for maintenance.
sudo dbctl instance db1138 depool sudo dbctl config commit -m "Depool db1138 T304933"
- Apply outstanding schema changes to db1138 (if any) T304933#7847187
- Update/resolve this ticket.